1. Field of Invention
This invention relates to an internal combustion engine in which two intersecting, toroidal cylinders are oriented perpendicularly to each other so that the enclosed pistons, which rotate uni-directionally and continuously at essentially uniform speeds, can additionally function as valves during all parts of a four-stroke cycle.
2. Prior Art
The inventor is unaware of any prior art involving internal combustion engines employing either the physical layout or the topographic principles presented in this disclosure.
However, a number of individual features relate to other internal combustion engines, in particular to toroidal or toroidal cylinder engines. Toroidal engines represent a subset of rotary engines in which the pistons trace either an arc or a full circle within one or more hollow toroidal chambers, the chambers of which act as hollow, doughnut-shaped cylinders. The patent office has not yet developed a rigorous classification system for defining the various types of toroidal engines, but a number of different types are known.
In one type, the pistons move back and forth with a scissoring action, as in U.S. Pat. No. 7,182,061. A central goal of the present invention is to avoid reciprocating motions and the well-known disadvantages inherent in such motions. A second subclass includes pistons that co-rotate at different speeds within a toroid such that when they approach one another, they compress the enclosed gas between them, and then after ignition, they move apart again due to the expanding gases. A common disadvantage of this type of engine is that the piston motions are variously intermittent, and in some cases one or more pistons come to a complete stop during a cycle. An example of this type of engine is U.S. Pat. No. 6,341,590. A third subclass is represented by U.S. Pat. No. 6,546,908. This particular engine has a single toroidal cylinder and a set of rotating pistons. A rotating disk valve perpendicular to the toroid has a cutout that periodically traverses the chamber to allow the passage of the pistons. The pistons compress air against the valve while approaching, then a cutout in the valve allows the piston to pass through, and then the valve face forms a back wall of the combustion chamber immediately after the piston's passage. As pointed out in this patent, the usual problem with this type of design is that the compressed charge typically loses its pressure because the valve mechanisms are too slow at high speeds.
Unlike other toroidal engines, in the embodiment presented here, each cylinder has only one piston. Each piston rotates uni-directionally, continuously, and at an essentially uniform rate. There is no alternating advancement of the pistons or vanes, and there is no cutout valve. The compressed charge is produced in an independent cylinder (torus) for storage in the combustion chamber. As the motion of the piston about to begin its power stroke is not involved in compressing the charge, high combustion ratios can be achieved. There are a number of additional advantages unique to this particular engine. Some of these advantages are common to toroidal engines in general. However, the principal object of this invention was to overcome some of the shortcomings and inefficiencies found in conventional engines.
The efficiency of any engine can be improved in two general areas: thermal efficiency and mechanical efficiency. With regard to thermal efficiency, A. Beau de Rochas set out the four classical principles for the best working conditions in a heat engine. This is the area where the greatest losses occur in a conventional engine.
(1) Employ the largest cylinder volume and the smallest exposed surface area. This design reduces the surface-to-volume ratio at the beginning of the combustion cycle by about half compared to that of a high-compression engine of equal displacement that has a main combustion chamber with a flat to lenticular shape. The greatest heat losses occur when the temperature differences are greatest, so it is during the early part of the combustion cycle that this lower surface-to-volume ratio is most important. The advantages of this reduced surface-to-volume ratio may go beyond simple heat losses. Combustion chambers with higher surface ratios may protect a relatively greater amount of gas bound to the surface layers from complete combustion. It is likely that the combustion chamber of a piston valve engine can be configured for high efficiency because it is naturally compact, and there are plentiful opportunities for turbulent motions within the gas without concern about the stopping and reversal of the piston's motion.
(2) Maximize possible piston speed. In a conventional engine, the piston is essentially stalled out at the beginning of the power stroke beyond TDC, just at the time when the heat energy can be most readily lost. In this design, the pistons are always at full speed. Thus, the duration or period of time in which the greatest heat losses can occur is greatly reduced.
A corollary, or a second important way of looking at this principle, might be that an engine should be run at high rpm's. By limiting the time frame, this also reinforces the point of having the fuel's heat energy go into expanding the gases rather than into the cylinder walls. High rpm's become self-defeating in a reciprocating engine, but no such mechanical impediments exist in this design.
(3) Use the highest possible pressures at the beginning of the power stroke. If this engine were to be used as a diesel, it could, in principle at least, employ higher compressions because the forces are reduced for a given pressure. In a conventional engine, the forces transmitted by the connecting rod may be limiting, especially if the bore is large. This engine achieves the same amount of work using smaller forces over a longer distance. If this general design were to be used in a spark-ignition engine, the compression ratio could, again in principle at least, possibly be increased over that seen in conventional engines, because the limitations due to the induction of knocking should be reduced. The fast moving piston might allow the flame-front space to propagate without inhibition, thereby forestalling the auto-ignition of unburned end-gases.
(4) Use the greatest possible expansion. Conventional engines preferably use a relatively short stroke to limit piston wall friction and for mechanical reasons due to the linkages. More importantly, the effective stroke is further shortened because the exhaust valves typically open up well ahead of BDC in order to facilitate gas movement. This compromise is justified in terms of overall performance. The fact remains, however, that heat losses through exhaust gases represent one of the greatest losses in the whole operation of a conventional engine. In this design, there is practically no concern over the facility with which gases can be expelled because of the huge cross-sectional area of a valve-less exhaust port. A piston valve engine can clearly take advantage of this principle, and providing smooth, high rpm's while extracting more of the fuel's energy. The increase in effective stroke length can easily be 25 percent compared to a conventional engine, and possibly more.
It appears that a piston valve engine may be superior on every count.
There are possibly other advantages to the management of heat in a piston valve engine. A conventional engine uses each cylinder as an all-purpose chamber, so, for example, the cylinder walls inappropriately heat cool air during the intake cycle. In contrast, a piston valve engine largely isolates the hot and cold processes, and because of the one-way airflow, can more closely approach a steady state of thermal equilibrium. Because the intake and exhaust ports are at the opposite end from the combustion chambers, a water jacket can easily encompass and precisely control temperatures in a manner appropriate to each area, especially the combustion area.
Improving mechanical efficiency is tantamount to reducing friction. Small gains might be realized by reducing the number of moving parts. The piston valve engine eliminates camshafts, valve train mechanisms, connecting rods, and the crankshaft. In actuality, the losses due to these components are small. Nonetheless, the core of a piston valve engine is vastly simplified and its moving parts are reduced to basically three unitized assemblies: two piston assemblies and an output shaft assembly.
In a conventional engine, the biggest frictional losses by far are due to pumping air. In vehicular applications, this can even exceed the outside aerodynamic losses (Argonne National Laboratories tests, 2006). It is in the area of pumping air where the greatest mechanical efficiency gains might be found, and this is another area where a piston valve engine excels. There are no intake or exhaust valves or constricted ports. Both the intake and the exhaust ports have unrestricted, immediately direct access to the atmosphere through huge, permanent openings. The areas of the port openings can exceed the areas of the piston heads, if desired. Although the route of airflow is different from that of the pistons, the movement of the pistons and the airflow are both one-way within each cylinder, therefore both movements facilitate higher rpm's and the circulation of gases, rather than counter them.
With regard to all of the numerous, external components of the engine, such as water pumps, oil pumps, fuel pumps, air pumps, fans, alternators, belts, and so forth, these are practically identical, or exactly identical, with those found on conventional engines. Most of these items represent only a fraction of a percent of engine losses.
Another very important advantage of the piston valve engine is that it has two ignition sequences per cycle (two pistons, but each with full and complete four-stroke functionality in one revolution). Horsepower is doubled, as it is directly proportional to the firing rate. However, the increase in efficiency and the increase in power-to-size ratio go beyond this. A conventional engine of two liters displacement, or more, will typically divide this among four cylinders, or more, for smooth operation. In a piston valve engine, practically any amount of displacement can be handled with the two cylinders, and it will still operate smoothly. This also means the total surface-to-volume ratio during combustion can be improved even further, benefiting the thermodynamic efficiency. At the same time, frictional losses from pumping air are proportionately reduced.
Other features include compact size for higher displacements, high output-to-weight ratio, and the absence of a flywheel. In this design, the pistons and the output shaft also function as the flywheel. The pistons can be built relatively heavy with little or no detriment to performance because their speed and inertia are essentially constant. The whole piston assembly actually encompasses a full 360 degrees and is dynamically balanced. Subsequent sections will detail further objects and advantages. Experts will think of other advantages inherent in the overall design.